Application of Bismuth Oxychloride as a Colorimetric UV Sensor Material

Sunlight contains about 9% UV radiation with roughly one-third of it penetrating the atmosphere and reaching the Earth’s surface. UV radiation from the sun is classified into three different types: UVA (315- 499 nm), UVB (280- 314nm), and UVC (100- 279 nm). Prolonged exposure to artificial UV radiation or direct sunlight can still induce many adverse effects such as sunburn, weakening of the immune system, and skin cancer. A wide variety of photoresistor, photodiode and colorimetric UV sensors are currently being researched to help monitor UV radiation. Our research is focused on developing a colorimetric UV sensor that is inherently safe and environmentally friendly and is composed of bismuth (III) chloride (BiCl3) and 6-carboxyfluorescein (6-CF). Two different UV sensors were prepared, a solution state with ethanol and a solid-state with a Grade 597 Whatman filter paper substrate. Our proposed mechanism involves the spontaneous hydrolysis of BiCl3 in ethanol to produce bismuth oxychloride (BiOCl). Upon UV exposure, BiOCl is excited and changes color from white to black. This extent of black color formation provides a direct measure of UV exposure. Other dye molecules including 5-Carboxyfluorescein (5-CF), prussian blue (PB), and rhodamine-b (RhB) were also tested. The 6-CF/BiCl3 solid-state sensor is very cheap and easy to scaleup production due to the filter paper substrate and readily available chemicals. The work presented here paves the way for a commercially viable sensor that is cheap to produce and more importantly easy to analyze the results leading to wide variety of applications across multiple industries.